Regenerative heat exchanger

ABSTRACT

A regenerative heat exchanger operable with a circulating pourable charge, which comprises pourable charge receiving columns having gas-permeable walls and being arranged one above the other while the upper column is passed through by a heatreleasing medium in cross counterflow and the lower column is passed through by a heat absorbing medium in cross counterflow, the columns which extend perpendicularly between two or more coaxial hollow cylinders or passages of a polygonal shape have a rectangular cross section and are substantially evenly spaced along said hollow cylinders, flow-guiding inserts being provided in the space between said columns and extending from wall to wall of said columns while guiding the heat-releasing medium and the heat-absorbing medium at an acute or right angle with regard to the direction of flow of the pourable charge in said columns.

United States Patent 1 mamas [72] Inventor Willibald Kraus 21756;? 6/1538 Forkel 165/107 Grebenstein, Germany 3,488,042 I/ 1970 Brzozowski et a 263/19 [21] AppLNo. 9,492

[22] Filed Feb. 9, 1970 [45] Patented Dec. 28, 1971 [73] Assignee Rheinstabl Henscbel Alttiengesellscbaft Kassel, Germany [32] Priority Feb. 8, 1969 Germany [54] REGENERATIVE HEAT EXCHANGER Primary Examiner-Edward G. Favors Attorney-Walter Becker dicularly between two or more coaxial hollow cylinders or passages of a polygonal shape have a rectangular cross section and are substantially evenly spaced along said hollow cylinders, flow-guiding inserts being provided in the space between said columns and extending from wall to wall of said columns while guiding the heat-releasing medium and the heat-absorb ing medium at an acute or right angle with regard to the direction of flow of the pourable charge in said columns.

Patented Dec. 28, 1971 3,630,500

2 Sheets-Sheet l Patented Dec. 28, 1971 2 Sheets-Sheet 2 l L a ar-riff;

REGENERATIVE HEAT EXCHANGER The present invention concerns a regenerative heat exchanger with continuously circulating pourable charge which is adapted to be controlled in mass flow and includes columns of pourable material arranged one above the other and communicating with each other while being confined by gas-permeable walls, the arrangement being such that the upper column of pourable material is passed through by a medium which gives off heat whereas the lower column of pourable material is passed through by a medium absorbing heat, the said media passing through the columns in a cross counter flow.

In the heat exchanger art, the heat exchange between flowing gases and pourable charges has been of importance for quite sometime. Under the term pebble heater" devices are known in which a pourable charge flows through two superimposed shaftlike heat exchanger chambers. The charge is heated in the upper chamber by heat releasing gases and is cooled again in the lower chamber by heat absorbing gases. With these devices, the pressure loss at the gas side will be all the greater thehigher the speed and the higher the pouring height is in the direction of the gas flow. If the heat output and the temperature differences are given, the height of the charge in the direction of the gas flow is all the greater the smaller the cross section and the higher the gas velocity is. If with relatively great gas flows in combination with relatively small temperature differences, a situation as it is encountered, for instance, with flue gas heated air preheaters in the steam generating art, the pressure losses are to be kept within customary limits, it is necessary that the required afflux cross section isavailable. Heretofore known heat exchangers working in the above-described manner have the following disadvantages which, depending on the respective type of construction, occur individually or in combination with each other:

a. they are suitable only for relatively small gas flows,

b. they are suitable only for relatively high temperature differences,

c. they are structurally expensive,

d. the pouring height is nonuniform over the cross section,

e. the times required for the individual charges to pass through the heat exchanger differ in part considerably,

f. the transporting device for the charge is liable to quick wear.

It is, therefore, an object of the present invention to provide a heat exchanger of the heat stone heater (Warmestein-Erhitzer) type which will be adapted in spite of a simple construction tofiealize higher and highest outputs per unit and to yield considerable advantages with regard to its own energy requirement, wear and lower pressure losses.

These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawings, in which:

FIG. 1 is a longitudinal section through a heat exchanger with belt pocket conveyor. FIG. 2 is a cross section through a heat exchanger with two concentric hollow cylinders and interposed columns of pourable charges.

FIG. 3 is a cross section through a heat exchanger with three concentric hollow cylinders and interposed columns of pourable charges.

FIG. 4 represents a diagrammatic illustration of the development of the columns of pourable charges with flowguiding inserts and helical upward flow of the medium.

FIG. 5 diagrammatically illustrates a development of the columns of pourable charges with horizontal flow-guiding inserts.

The heat exchanger according to the present invention is characterized primarily in that perpendicularly between two or more concentrically arranged hollow cylinders or multicornered passages it is possible to provide columns of pourable charges having a longitudinally extending rectangular cross section so that the columns extend radially while being circumferentially evenly or approximately evenly distributed. The heat exchanger according to the invention is furthermore characterized in that the passages between the columns are adapted to be subdivided by a plurality of superimposed flowguiding inserts which extend from wall to wall and at an acute or a right angle with regard to the direction of flow of the heat releasing and heat-absorbing medium. A uniform feeding of the pourable material to the columns of pourable material will be assured by connecting the radially arranged columns of pourable material with a centrally arranged funnel-shaped container above said columns through feeding pipes while said columns are connected with a funnel-shaped container below said columns through discharge pipes. In order to prevent as far as possible the development of heat tensions in the heat exchanger, it is provided that the gas-permeable walls of the individual columns are fixedly connected to the upper funnelshaped container while the individual columns are movably guided laterally as well as at their junction with the lower funnel-shaped container. The charge is, in conformity with the present invention, kept in circulation by means of a pocket conveyor which moves in a passage extending symmetrically around the outer mantle of the heat exchanger and conveys the pourable charge or material from the lower container to the upper container. The speed at which the pourable material passes through the columns may be varied by means of a device arranged in the outlet chute of the lower container for continuously adjusting the discharge cross section. In order to prevent the conveyor from being subjected to undue heat stresses, the medium to be heated bay be passed through the passage in which the conveyor is guided.

Referring now to the drawings in detail, the arrangement shown therein comprises superimposed columns I of pourable charges which are interconnected by means of overflow pipes 37. The charge is supplied from the funnel-shaped container 33 through the upper feeding pipes 34. The discharge of the pourable charge is effected through discharge pipes 40 into the funnel-shaped container 41 from where the charge passes through a device for continuously adjusting the discharge cross section 43 into the lower discharge passage 26. By means of a conveyor equipped with a pocket-containing belt 24, the pourable charge is from the lower discharge passage 26 conveyed back to the upper funnel-shaped container 33.

FIG. 2 shows the radial arrangement of the individual columns of pourable charges which columns are confined by the concentric hollow cylinders 4 and 5. The gas-permeable lateral confining walls 3 of said columns I are both sides guided between the guiding strips 7 on the hollow cylinders 4 and 5 in such a way that the confining walls 3 which, in conformity with FIG. 1, are connected to the upper funnel-shaped widened section 35 can freely expand in downward direction. The columns I are arranged radially and are substantially evenly spaced along the circumference of the concentric hollow cylinders 4, 5 and 6. The free cross sections 8 between the individual columns 1 are approximately equal.

According to the embodiment illustrated in FIG. 4, a triple cross counter flow is produced due to the fact that the medium is by means of flow guiding inserts 9 between the columns I along the direction indicated by the arrows l0 guided along helical lines with such a pitch that each helical line intersects three vertical columns I at different levels.

According to the embodiment illustrated in FIG. 5, a triple cross counter flow is realized due to the fact that on the medium entrance side between the columns 1 each second cross section 8 is covered by a horizontal flow-guiding insert 11. The medium flows through the free cross sections 8 vertically in the direction of the arrows 12 between each two columns 1 in upward direction and by means of said horizontal flow-guiding inserts 11 in these passages is forced to split up according to the direction of the arrows l2 and to flow at both sides approximately horizontally through the columns I. The partial flows will, after the first passage through the columns I in conformity with the direction of the arrows l2 unite with one adjacent partial flow each and mix therewith, and the thus united flow will pass vertically upwardly until it is forced by the horizontal flow-guiding inserts 11 to split up again and to flow at both sides approximately horizontally through the columns 1. The lines along the direction of the arrows 12 indicate the path of flow of the medium. The number of the columns 1 is in this instance an even number. From the longitudinal section through the heat exchanger according to FIG. 1 it will be seen that the inner hollow cylinder 4 has a greater diameter than the length of the longitudinally extending rectangular base surface of a column 1. In this way it is possible that, in case of a necessary repair, a column 1 can be exchanged from the inside of the hollow cylinder 4 which is accessible by the repairman.

If the heat exchanger illustrated in FIG. 1 represents an air preheater which follows a boiler, the upper columns 1 are passed through by heat-releasing flue gases, and the lower columns 1 are passed through by heat-absorbing combustion air. The preheated combustion air will in the illustrated example pass along the direction of the arrow 14 vertically upwardly through the inner hollow cylinder 4 and eventually horizontally outwardly through the cross section 15. If the steam boiler is equipped, for instance, with a ceiling firing system, this arrangement will result in a saving with respect to the necessary hot air passage.

in view of the heat expansions, it is advantageous to suspend the columns 1 as well as the concentric confining passages (hollow cylinders) 4, 5 and 6 with the guiding strips 7 at their upper end so that they can freely expand in downward direction. According to FIGS. 2 and 3 there is provided an outer hollow cylinder 16 into which the vertical forces can be introduced through a plate 17 or tunnel 18 (FIG. 1). High temperatures will be kept away from the supporting outer mantle 16 by a heat insulation 19 between the hollow cylinders 5, 6 and 16. The supporting outer mantle or hollow cylinder 16 may be dimensioned sufficiently large so as to be able, if necessary, also to support a mounted chimney 20 according to FIG. 1. In the embodiment illustrated in FIG. 1, the flue gas passes from the outside into the free chamber 21 and from here, in conformity with FIGS. 4 and 5, as mentioned above, into the chamber 22 and through the free cross sections as both sides of the tunnel 18 through passages 23 at both sides into the chimney 20 and from there into the atmosphere.

FIGS. 1, 2 and 3 illustrate an embodiment for the circulation or lifting of the charge of pourable material. The conveyor 24 equipped with pockets 24a is arranged symmetrically around the outer supporting mantle 16. The pockets of the conveyor 24 do not carry out a scooping action, but the pourable material flows into said pockets from the inside of the heat exchanger. This greatly extends the life of the pourable material. The conveyor 24 is surrounded by rectangular shafts 25. In the particular embodiment illustrated in FIG. 1, combustion air passes through the shafts 25 in the direction of the arrows l4 first in downward direction to cool the conveyor 24. The combustion air then passes through the free cross sections 27 into the chamber 28 and from here, in conformity with FIGS. 4 or 5, into the chamber 29 and further through the free cross sections 30 into the inner hollow cylinder 4 and upwardly as described above. The inner hollow cylinder 4 is sealed toward its bottom portion by a partition 31. The chambers 21 and 29 are separated from each other by a partition 32.

All radially arranged columns 1 are fed from an upper centrally arranged funnel-shaped container 33. Container 33 forms the lower extension of the tunnel 18 through which the conveyor belt 24 is passed and into which the upwardly conveyed pourable material is dumped. From the container 33 the pourable material passes through the upper feeding pipes 34 and funnel-shaped widened sections 35 into the upper columns 1. The upper and lower columns 1 are interconnected by funnel-shaped constrictions 36, overflow pipes 37 and funnel-shaped widened sections 38. From the lower columns 1, the pourable material passes through funnelshaped constrictions 39 and the lower discharge pipes 40 into the lower centrally arranged funnel-shaped container 41. Simplifications as to the manufacturing process are obtained due to the fact that for the upper feeding pipes 34, the overflow pipes 37 and the lower discharge pipes 40, pipes with square cross section are employed. The lower discharge pipes 40 are at the bottom side of the inclined section provided with longitudinal slots according to FIG. 1 so that at these areas the abrasion or dust of the pourable material can separate from the circulating material. The width of the slot is less than the shortest diameter of the bodies of which the pourable material consists. At the lower discharge openings of the columns 1 there are provided in the funnel-shaped tapering sections 36 and 39 inserts 42 for equalizing the throughflow of the pourable material.

Inasmuch as all radially arranged columns 1 are being fed centrally from the center and come together at the lower end at a central point, the flow conditions for all columns are the same.

Built into the discharge chute of the lower funnel-shaped container 41 is a device 43 for infinitely varying or adjusting the discharge cross section. This device permits the adaptation of the installation to the changing conditions of operation. Similarly, means are provided for infinitely varying the driving speed of the conveyor.

In order to permit an occasional purification of the circulating pourable material, the lower funnel-shaped container 41 has, in conformity with FIG. I, built-in a washing device 44. The rubber belt 24 is provided with perforations which are smaller than the smallest pourable body to allow the water to drain off.

As will be seen from the above, an arrangement according to the present invention has, among others, the advantage that the heat exchanger will in view of the round cross sections be particularly suitable for higher overpressures of the medium. Moreover, with a rather simple construction, higher and even highest outputs per unit can be realized.

When employing the heat exchanger as an air preheater following a steam boiler with ceiling firing system, the costs for the hot air passage will be reduced.

it is, of course, to be understood that the present invention is, by no means, limited to the particular showing in the drawings but also comprises any modifications within the scope of the appended claims.

What 1 claim is:

l. A regenerative heat exchanger operable with a circulatory pourable charge, which includes: upper container means arranged at the upper portion of said heat exchanger and adapted to receive a pourable charge, a plurality of ductshaped column means arranged one above the other and in communication with each other, feed conduit means establishing communication between said upper charge receiving means and the uppermost column means, lower container means arranged at the lower portion of said heat exchanger below said column means for receiving pourable material therefrom, the walls of said duct-shaped column means being gas permeable, first conveying means for conveying a heat-releasing medium through said upper column means in counter crossflow to the flow of the pourable material in said upper column means, second conveying means for conveying a heat absorbing medium through the lower column means in counter crossflow to the flow of the pourable material in said lower column means, and at least two substantially coaxially arranged tubular bodies, all of said column means being arranged between and extending radially with regard to said tubular bodies while defining passages therebetween and being substantially evenly distributed with regard to the circumference of said tubular bodies, said first and second conveying means including flow-guiding means arranged in said passages and extending from the wall of one column to the wall of the respective adjacent column.

2. A heat exchanger according to claim 1, in which at least some of said flow-guiding means extend at an acute angle with regard to the direction of the vertical axis of said heat exchanger to thereby provide a helical path for the medium passing through said passages.

3. A heat exchanger according to claim 1, in which at least some of said flow-guiding means extend at a right, angle with regard to the direction of the vertical axis of 7 said heat exchanger to force the medium passing through said passages to move partially alonghorizontal paths.

4. A heat exchanger according to claim 1, in which said duct-shaped column means have a rectangular cross section.

5. A heat exchanger according to claim 4, in which the inner diameter of the innermost tubular body is in excess of the cross-sectional length of said columns.

6. A heat exchanger according to claim 1, which includes feeding conduit means connecting said upper container means with the adjacent column means, and also includes discharge conduit means connecting said lower container means to the adjacent column means.

7. A heat exchanger according to claim 1, in which said upper container means is funnel-shaped while tapering in downward direction, and in which the gas-permeable walls of the column means are fixedly connected to said funnel-shaped upper container means and in which said gas-permeable walls of said column means are slidably connected to said lower container means.

8. A heat exchanger according to claim 1, which includes conveyor means movable around said column means and said upper and lower container means, said conveyor means being provided with pockets passing below said lower container means and being adapted to receive pourable material collected in said lower container means from the latter in free fall from said lower container means, said pockets also being adapted when passing over said upper container means to dump the contents of the respective pockets into said upper container means.

9. A heat exchanger according to claim I, in which said lower container means is funnel-shaped and is provided with an outlet and also with control means associated with said outlet for varying the cross section of said outlet.

10. A heat exchanger according to claim 8, which includes passage means surrounding and guiding said conveyor means, said passage means being provided with inlet means at the upper end of said heat exchanger for receiving the medium to be heated, said passage means also being provided with outlet means near the lower end of said column means for conveying the medium received in said passage means from the latter to the lower column means. 

1. A regenerative heat exchanger operable with a circulatory pourable charge, which includes: upper container means arranged at the upper portion of said heat exchanger and adapted to receive a pourable charge, a plurality of duct-shaped column means arranged one above the other and in communication with each other, feed conduit means establishing communication between said upper charge receiving means and the uppermost column means, lower container means arranged at the lower portion of said heat exchanger below said column means for receiving pourable material therefrom, the walls of said duct-shaped column means being gas permeable, first conveying means for conveying a heat-releasing medium through said upper column means in counter crossflow to the flow of the pourable material in said upper column means, second conveying means for conveying a heat absorbing medium through the lower column means in counter crossflow to the flow of the pourable material in said lower column means, and at least two substantially coaxially arranged tubular bodies, all of said column means being arranged between and extending radially with regard to said tubular bodies while defining passages therebetween and being substantially evenly distributed with regard to the circumference of said tubular bodies, said first and second conveying means including flow-guiding means arranged in said passages and extending from the wall of one column to the wall of the respective adjacent column.
 2. A heat exchanger according to claim 1, in which at least some of said flow-guiding means extend at an acute angle with regard to the direction of the vertical axis of said heat exchanger to thereby provide a helical path for the medium passing through said passages.
 3. A heat exchanger according to claim 1, in which at least some of said flow-guiding means extend at a right angle with regard to the direction of the vertical axis of said heat exchanger to force the medium passing through said passages to move partially along horizontal paths.
 4. A heat exchanger according to claim 1, in which said duct-shaped column means have a rectangular cross section.
 5. A heat exchanger according to claim 4, in which the inner diameter of the innermost tubular body is in excess of the cross-sectional length of said columns.
 6. A heat exchanger according to claim 1, which includes feeding conduit means connecting said upper container means with the adjacent column means, and also includes discharge conduit means connecting said lower container means to the adjacent column means.
 7. A heat exchanger according to claim 1, in which said upper container means is funnel-shaped while tapering in downward direction, and in which the gas-permeable walls of the column means are fixedly connected to said funnel-shaped upper container means and in which said gas-permeable walls of said column means are slidably connected to said lower container means.
 8. A heat exchanger according to claim 1, which includes conveyor means movable around said column means and said upper and lower container means, said conveyor means being provided with pockets passing below said lower container means and being adapted to receive pourable material collected in said lower container means from the latter in free fall from said lower container means, said pockets also being adapted when passing over said upper container means to dump the contents of the respective pockets into said upper container means.
 9. A heat exchanger according to claim 1, in which said lower container means is funnel-shaped and is provided with an outlet and also with control means associated with said outlet for varying the cross section of said outlet.
 10. A heat exchanger according to claim 8, which includes passage means surrounding and guiding said conveyor means, said passage means being provided with inlet means at the upper end of said heat exchanger for receiving the medium to be heated, said passage means also being provided with outlet means near the lower end of said column means for conveying the medium received in said passage means from the latter to the lower column means. 